ISP1521 Datasheet, PDF (44/53 Pages) NXP Semiconductors – Hi-Speed Universal Serial Bus hub controller

Philips Semiconductors
ISP1521
Hi-Speed USB hub controller
17. Application information
17.1 Descriptor configuration selection
upstream
facing port ^GoodLink
ROM
ISP1521
I²C-bus
green and
amber LEDs,
port 1
..
green and
amber LEDs,
port 7(1)
7 USB downstream facing ports
external microcontroller
acting as I²C-bus master
USB function
EEPROM
004aaa302
The I²C-bus cannot be shared between the EEPROM and the external microcontroller; see Table 11.
(1) The function on port 7, which is a non-removable port, is optional.
Fig 17. Descriptors configuration selection application diagram.
17.2 Overcurrent detection limit adjustment
For an overcurrent limit of 500 mA per port, a PMOS with R_DSON of approximately
100 mΩ is required. If a PMOS with a lower R_DSON is used, analog overcurrent
detection can be adjusted by using a series resistor; see Figure 18.
∆V_PMOS = ∆V_trip = ∆V_{trip(intrinsic)} − (I_OC(nom) × R_td), where:
∆V_PMOS = voltage drop on PMOS
I_OC(nom) = 0.6 µA.
5V
9397 750 13702
Product data
VREF(5V0)
IOC
Rtd(1)
PSWn_N OCn_N
ISP1521
004aaa260
(1) R_td is optional.
Fig 18. Adjusting analog overcurrent detection limit (optional).
Rev. 03 — 24 November 2004
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
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